Conventionally, with general fuel supply apparatuses, a throttle valve is provided on an intake passage extending toward an engine from an air cleaner and an injector for jetting of a fuel is arranged downstream of the throttle valve in an air current direction (referred below to as “downstream injector”).
On the other hand, there is a fear that a fuel feed rate becomes short only with a downstream injector at the time of high rotation/high load of an engine. Therefore, an injector is in some cases arranged in an air cleaner connected to an upstream side of an intake passage in the air current direction (referred below to as “upstream injector”). In many cases, such upstream injector is provided in a state of projecting into the air cleaner in order to ensure a volume for the air cleaner and to reduce a distance between the upstream injector and an opening of the intake passage. A fuel is jetted not only from the downstream injector but also from the upstream injector at the time of high rotation/high load of the engine.
Such construction, that is, a construction, in which an injector is arranged in a space upstream of the intake passage, is disclosed in, for example, Patent Document 1. With the construction disclosed in Patent Document 1, an injector is mounted in a chamber connected to an upstream side of an intake pipe.
More specifically, with the construction disclosed in Patent Document 1, a mount seat surface for mounting of an injector is formed on a side wall of the chamber. The mount seat surface projects into the chamber and the projecting portion thereof is formed with a hole. The injector mounted to the mount seat surface jets a fuel into the chamber through the hole.
Patent Document 1: JP-A-7-247924